IN the observations which I have made on animals passing into death by the lethal process, nothing has impressed me more than the curious differences of vitality or vital values of different animals. The differences are so great they seem almost inexplicable, and in many respects they are so. To some extent, however, they come under law, and we may therefore hope that by carefully continued research what is now difficult and involved may be rendered, in time, simple and perfectly clear.

The first series of observed facts relate to vital differences in animals of different species. In illustration I may take the cat and the dog. Between these animals the distinction of vitality exists irrespectively of age, and of all other conditions and circumstances of which I can gather information.

Of the cat it is commonly said that it has nine lives. By this saying nothing very definite is meant beyond the opinion that under various kinds of death the cat lives much longer than other animals that have to be killed by violent means. When any question is asked of the police or of other persons who have to take the lives of lower animals, they tell you, without exception, according to my experience, that the cat is the most difficult to destroy of all domestic animals, and that it endures accidental blows and falls with an impunity that is quite a distinguishing characteristic.

The general impression conveyed in these views is strictly correct up to a certain and well-marked degree. By the lethal death, the value of the life of the cat is found to be, at the least, three times the worth of the dog. In all the cases I have seen in which the exactest comparisons were made, the cat outlived the dog. A cat and dog of the same ages being placed in a lethal chamber, the cat may, with perfect certainty, be predicted to outlive the dog. The lethal chamber being large enough to hold both the cat and the dog, the vapor inhaled by the animals being the same, with every other condition identical, this result, as an experimental truth, may be accepted without cavil.

The differences, always well marked, are sometimes much longer than would be credible in the absence of the evidence. I have once seen a cat, falling asleep in a lethal chamber in the same period as a dog, remain breathing, literally, nine times longer, for the dog died within live minutes, and the cat not only continued to breathe, in profoundest sleep, for forty-five minutes, but would have been recoverable by simple removal from the vapor into fresh air if it had been removed while yet one act of breathing continued. This, however, was exceptional, because the cat in the same lethal atmosphere as the dog does not, as a rule, live more than thrice as long; i. e., if the dog ceases to breathe in four minutes, the cat will cease in from ten to twelve minutes after falling asleep.

The character of the vapor used does not make any difference, relatively. Carbonic oxide, carbonic acid, chloroform-vapor, carbon bisulphide vapor, yield the same relative results. Pure carbonic oxide kills with intense rapidity, but it kills the cat less quickly than the dog. If instead of a lethal vapor prussic acid be used, in administration by the mouth, the cat dies more slowly than the dog. The same is true in respect to death by drowning.

Still more curiously, recovery from apparent death is much more frequent in the cat than in other domestic animals. Mr. Warrington once observed a cat recover from apparent absolute death by prussic acid, eight hours after it had lain as if dead. I once saw a young cat come back to life after two hours of immersion under cold water.

I do not know many facts bearing on tenacity of life in other animals, but I have observed that sheep in a lethal atmosphere die very rapidly, goats much less rapidly, and pigeons more rapidly than common fowls. There is, apparently, a specific tenacity in all species.

In animals of the same species there are distinctions determinable by peculiarities in the animal itself. In one instance where a large number of dogs were put to sleep in the lethal chamber, one was found in deepest sleep, but still breathing, side by side and partly covered by another that was not only dead but cold and rigid. A similar fact occurred last year in the human subject in a mine. A father and son killed by fire-damp lay together, the father dead, the son living, though he, the son, had come first under the influence of the lethal gas. In all the fatal accidents to the human subject from the administration of chloroform or other narcotic vapor we see the same illustration. I doubt whether in any one of these unhappy events the death has been induced by what would be, under the common run of administrations, a fatal dose. But some die from a dose that would not so much as narcotize others. An analogous series of facts is met with in relation to the effects of physical and mental shocks and to surgical operations.

The variation of measure of tenacity of life is unquestionable. What is the reason of it? What is there in one species of animal that gives a measure of tenacity over another? Why, for instance, is the cat more tenacious of life than the dog?

The only answer as yet is, that the cat is endowed with more vitality. But this is no answer as to details. Is the endowment of the greater vitality centered in the nervous system, in the muscular, in the respiratory, in the blood, in the membranes?

And wherever centered, what is the endowment?

The difference of tenacity in animals of the same species is more approachable, because we know certain factors that afford an explanation of it.

Age is a factor. In the young the tenacity is more distinctly marked than in the old. In a broad sense there is no exception to this rule.

Degenerations of tissues are factors. Fatty degenerations are reducers of tenacity. Lessened arterial tension is a reducer.

Race or breed is another factor. The strong, wiry, muscular animal of any species is more tenacious of life than the heavier and less elastic. The terrier outlives the spaniel or retriever. The man of sanguine temperament outlives the nervous and lymphatic man.

In the operation of tracheotomy for croup or diphtheria in children, other things being equal, the chances of a successful issue will be as two to one to a spare, active, wiry subject compared with the chances of the full-cheeked, full-bodied child with luscious lips and rich flowing curls of pale or golden hue. The first of these will live almost through the gate of death; the second will succumb without a struggle for life.

Will is a factor. I have twice seen tenacity of life maintained, as it were, against all possibilities by what is called the will of the sufferer. Mr. F. Hall, of Jermyn Street, had a patient in the last stage of pulmonary consumption, whom I had seen with him in what appeared to be a condition of emaciation and exhaustion that precluded the feeblest effort toward rising from bed. Yet one day, and three weeks only before actual death, this sick man by a supreme effort of volition rose, dressed himself, went out of his house, and had to be sought for by his friends and brought back, with gentle compulsion, simply to die.

A young authoress of great promise, suffering from the same disease—pulmonary consumption—in the very last days of her life rose from bed, and in the most vigorous style was engaged for several hours in composition on letters and work which had been for months laid aside. Her friends, bewildered by the phenomenon, could scarcely accredit that the effort did not presage recovery, until rapid collapse dispelled the illusion.

This tenacity of life illustrated through volition is the equivalent of that courageous endurance which some in famine and war have "miraculously" exhibited.

These examples illustrate the influence of certain factors on tenacity of life, and they may, one day, lead up to the prime cause of the difference of tenacity if they and other facts bearing on the matter be carefully observed and recorded. But, as yet, the prime cause remains a troubled and troublous question.—The Asclepiad.